Pulpstone



United PULPSTONE LoringC'oes, In, Brookfield, and Marion S. Kraft, Princeton, Mass., assignors to Norton Company, Worcester, Mass., a corporation of Massachusetts Application December 4, 1956, Serial No. 626,187

8 Claims. (Cl. 51206.4)

The invention relates to pulpstones.

One object of the invention is to produce pulp that will make stronger paper. Another object is to produce pulp that will make paper of superior quality: finer finish, better surface, denser, opaquer, and less pervious.

Other objects will be in part obvious or in part pointed out hereinafter.

In the accompanying drawings illustrative of the invention,

Figure 1 is a diagrammatic development of a pulpstone according to the invention having two kinds of blocks,

Figure 2 is also a diagrammatic development of a pulpstone according to the invention having three kinds of blocks.

A pulpstone according to the invention can be of any mechanical construction. One very good construction and the one that we prefer is disclosed in U. S. Letters Patent to W. L. Howe and L. S. Washburn, No. 2,421,885 patented June 10, 1947. Many pulpstones constructed according to this patent have been manufactured, sold and used with satisfaction not only in the United States but in many foreign countries.

The pulpstone represented by Figure 1 has blocks of one kind 11 and blocks of another kind 12, while the pulpstone of Figure 2 has blocks of one kind 13, blocks of another kind 14 and blocks of a third kind 15. Pulpstone blocks are referred to in many patents as segments.

In order to make a stronger paper or a paper having finer finish, better surface, being denser or opaquer or less pervious or any combination of these, we provide a pulpstone that will make pulp having fibers of different coarseness or length. The pulpstone herein illustrated will do this, since blocks of different kinds produce pulp of fiber of different coarseness and length. With pulp of different kinds of fibers the fundamental objects of this invention are achieved.

One specification for any pulpstone is the kind of abrasive. The only abrasives that have been used up to now in the manufacture of pulpstone blocks are aluminum oxide and silicon carbide. There are many kinds of aluminum oxide, to Wit. natural corundum, emery, regular fused alumina, white fused alumina, and fused alumina produced in discrete crystals from a sulphide matrix. There are fewer kinds of silicon carbide but varieties have been identified as black, grey, and green.

According to this invention two pulpstone blocks are different if they are made of or have:

(a) Abrasive of different kinds,

(b) Different grit size of abrasive differing by at least as measured by the grit size number (not as measured by particle size), and

(c) Porosity in open interconnecting pores differing by at least 5% Whether a given case falls within or Without these definitions can be determined by simple arithmetic in a moment for (b) and (0). Whether the two abrasives are different or not is determined by applying the following rules seriatim:

. 2,810,995 Patented Oct. 29, 1957 green silicon carbide is different from either.

(3) The above mentioned aluminas are all of different kind. In the case of any other alumina, it is different from the other one involved if the hardness difference between the two is more than 40. on the Knoop 100 scale.

(4) Two zirconias are different as one is stabilized and the other is not. A zirconia is stabilized if its crystals are cubic or tetragonal, and is not stabilized if its crystals are monoclinic. of partially stabilized zirconias, the difference between the crystal categories must be at least 30% to make the zirconia different.

(5) In the case of all other abrasives, if they are of different materials, they are different as in (l), but if the abrasive is of the same material they are different if their hardness on the Knoop 100 scale is different by at least 50.

The blocks 11, 12, 13, 14 and 15 are identified by the following table:

TABLE I Abrasive Volume Percentage Block Of Open Grit and Inter- Kind Size connecting Pores Regular Alumina 36 37. 2 Green Silicon Carbide. 60 43. 0 Regular Alumina 36 48.7 14 Gray Silicon Carbide 34. 9 15 Green Silicon Carbide 60 40. 8

These blocks are further identified by the following table:

TABLE II Volume Percentage Vitrified of- Bond As Block Per U. S.

Patent No. Abrasive Bond In every case the bond is vitrified bond, this type of bond being well known and described in many patents. Sometimes it has been called ceramic bond. Other kinds of bonds have been found to deteriorate or to give inferior results in pulp grinding.

There is one more requirement for a pulpstone according to our invention in order to make pulp fibers sufficiently different in kind to make paper that is stronger or of superior quality as to finish, surface, density or opacity. That is that there be at least five blocks of tWo different kinds as defined in this specification. The fundamental objects of this invention are achieved according to our invention by providing a pulpstone having two categories of blocks and at least five of each category, and of course there will be more of one category or else there may be more than two different categories, and it suffices if two of many categories have each of them five blocks and that the blocks differ from each other as stated herein.

It will thus be seen that there has been provided by this invention a pulpstone in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as See U. S. Patent No. 2,535,526. In the case many 'changesmight be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

We claim:

. 1. A pulpstone having at. least. two difie'rentkinds, of pnlpstone blocks each block consistingof. abrasive bonded with vitrified bond, said pulpstone having at least five blocks of each kind, said blocks being different in at least one of the following particulars: kind of abrasive, grit 10 size of abrasive by at least as much as five percent of the grit size number, and porosity of open and interconnecting pores by at least 5%. v r

2. A pulpstone according to claimrl in which the difference between blocks is a difference in the kind of 15 abrasive.

3. A pulpstone according to claim 2 in which the difierence, between blocks-is a difierence as stated in the grit size of the abrasive.

4. A pnlpstone according to claim 3 in which the difierence between blocks is the ditference as stated in the porosity of open and interconnecting pores.

5. A pulpstone according to claim 1 in which the difference between the blocks is a difference as stated in the grit size of the abrasive.

6. A pulpstone according to claim 5 in which the difference between blocks is the difference as stated in the porosity of open and interconnecting pores.

7. A pulpstone according to claim 1 in which the difierence between blocks is the difference as stated in the porosity of open and interconnectin'g'pores.

8. A pulpstone according to claim 7 in which the difference between blocks is a difference in the kind of abrasive.

References Cited in the file of this patent UNITED STATES PATENTS 933,603 Waggn Sept. 7, 1909 

